In winter only about five species of fish larvae were collected and in summer they increased to about 30 species. Larvae of fishes were most abundantly collected during June to August and the eggs were abundant in the period of April to July. In winter both were scanty. The variations of total catch were subject to increment or decrement of the eggs or larvae of Sardinops melanosticta (T. et S.), Engraulis japonica (HOUTTUYN), Cololabis saira (BREVOORT) and Upeneus bensasi (T. et S.). Comparing with those in the adjacent waters of the Goto Islands, the period of occurrence in this area was shorter and later in most species, and several species were common in the Oki area but scarce in the Goto area. The dominant species were Sardinops melanosticta and Etrumeus micropus (T. et S.) in Spring, Engraulis japonica and Upeneus bensasi in summer, and Goniistius zonatus (C. et V.) (or G. quadricornis (GUNTHER)) and Labracoglossa argentiventris PETER in autumn.
Some ecological characters of individuals were compared among four populations of the almond moth. The populations were bred for about 20 generations under the experimentally controlled conditions. When the food was supplied at an interval longer than the mean length of a life cycle of the moth, the duration of the developmental period of the individuals becomes longer than that of the individuals in the population with short interval of food supply. The individuals in the population which had been parasitized with the Ichneumon wasp, Nemeritis canescens GRAV., become slower in their development and slightly lower in their susceptibility to the parasitoid wasp than the individuals in the population free from its parasitization. These differences of the ecological characters of the individuals among populations may be caused by the action of the different mechanisms of density regulation. The individual difference of the head width of the moth can not be seen among these populations.
Um die Beziehungen unter den Oribatidenzonosen, Pflanzendecken und Bodencharakteren zu suchen, wurde in Oku-Nikko-Gebirge eine zonologische Untersuchung durchgefuhrt. Als die Untersuchungsstellen wurden 18 Bestanden von verschiedenen Vegetationstypen, die im Untersuchungsgebiete typisch treten, gewahlt. Zuerst erscheinen hier Beschreibungen jeder Pflanzendecke und Bodenschicht bis zu 20cm Tiefe. Ferner sind die gefundenen Oribatidenarten und ihre Fundorten in einer Tabelle zusammenfassend hinzugesetzt.
Some laboratory experiments concerning food consumption were carried out on Strongylocentrotus intermedius. The animals eat a wide variety of sea-weeds. The daily amount of food eaten per adult specimen (ca. 50mm in test diameter) varied largely among different kinds of sea-weeds ; the largest amount of food eaten was about 3g in wet weight when supplied with Laminaria japonica and the lowest was about 0.5g in Ulva pertusa. These values correspond to respectivelly 6 per cent and 1 per cent of the body weight of the sea urchin. Marked decline in the daily amount of food eaten per adult specimen of sea urchin was between July and October, while such decline was not recognized in the young specimen. The above restriction of the feeding of the adult urchins may bs attributed to some physiological factors correlated with gonadal development. The daily rate of feeding decreased as the urchin grew larger. However, there was no significant difference of sea urchins of different size in their ability to assimilate the food eaten. Assimilation efficiency increases with rising water temperature and vice versa ; the mean value of assimilation efficiency was about 70 per cent in summer and about 55 per cent in winter, when Laminaria japonica was supplied as food for the sea urchins. The amount (in dry weight) of food (Laminaria japonica) assimilated kept a high level (ca. 270mg/day/individual)during February to June and fell to about 50mg/day/individual in September and October.
This paper deals with the incipient behaviors observed in the superindividual stage of Polistine wasps which follows the solitary stage, the first stage in their life cycle, characterized by nest founding by each solitary female (YOSHIKAWA 1962). With the eclosion of the first worker, the life cycle of Polistes enters into the superindividual stage which lasts until the eclosion of females of the next generation. Various behaviors observed in the early period of this stage are described. Special attention was paid on the process of formation of division of labor among workers. From that the phenomenon of nest evacuation occurs mostly immediately before the transition of the life of Polistes from the solitary stage to the superindividual stage, it was considered to constitute a crisis in the life cycle.
To assess the degree of water pollution in the Tokoro River, Kitami, Hokkaido, the benthic micro-organisms were studied and discussed according to the saprobic system. The river rises from Mt. Ishikari-dake and flows down through the Kitami Plain to the Okhotsk Sea. Samples were taken at seven stations in the lower half of the river in August, 1960 (see Fig. 1). Examining the predominant species found in each station and their status in the saprobic system, it is indicated that the river is rather clear and may belong to β-mesosaprobic waters (Table 1). The water is, however, contaminated considerably at Wakamatsu-bashi, Kitami City, where the waste water of palp mill flows in. The β-polysaprobic species become predominant in this station. The water quality recovers gradually to the α-or β-mesosaprobic level at the station Chushi-bashi, about 15km below Kitami City. Downstream, the stream maintains its β-mesosaprobic status until it flows into the sea. A map showing the degree of water pollution in various parts of the river was drawn from the data obtained in this study (Fig. 2).
The conditions under which the aquatic Hyphomycetes are distributed were studied in some Japanese lakes and rivers. There are two groups of aquatic fungi i.e. 1) the fungi inhabiting in running water and 2) that of in standing water. Marked differences are seen according to the differences in lake type. Tricladium gracile var. oxyphilum and Anguillospora longissima are distributed mostly in the acidotrophic lakes. Varicosporium elodeae and Tricladium gracile are the only species in the dystrophic lakes. On the other hand, Tetrachaetum elegans, Articulospora teraclodia and Lemonniera aquatica are the main fungi in the harmonic lakes.